To enhance the competitiveness of networks in the future, the 3rd Generation Partnership Project (3GPP) is studying a brand-new evolved network. As shown in FIG. 1, the system architecture of the evolved network includes: an evolved UMTS terrestrial radio access network (E-UTRAN), adapted to implement the radio access functions in the evolved network; a mobility management entity (MME), responsible for mobility management of the control plane, such as user context and mobile status management and allocation of temporary user IDs; a serving gateway (serving GW), which is the user plane anchor point between the 3 GPP access networks and also the interface for receiving the E-TURAN; and a packet data network gateway (PDN GW), which is the user plane anchor point between a 3GPP access network and a non-3GPP access network and also the interface for receiving the connection with external PDNs. A policy and charging rules function (PCRF) is adapted to make a policy control decision and exercise traffic charging control. A home subscriber server (HSS) is adapted to store subscription information of users.
A UMTS terrestrial radio access network (UTRAN) and a GSM/EDGE radio access network (GERAN) are adapted to implement the radio access functions in the current GPRS/UMTS network. A serving GPRS support node (SGSN) is adapted to implement functions in the GPRS/UMTS network, such as routing and forwarding, mobility management, session management, and user information storage.
Non-3GPP IP access networks are defined by some non-3GPP organizations. Such networks include a wireless local area network (WLAN), a worldwide interoperability for microwave access (WIMAX) network, and a code division multiple access (CDMA) network. The non-3GPP IP access networks are connected to a PDN GW and an authentication, authorization and accounting (AAA) server, where the AAA server is adapted to implement access authentication, authorization and accounting functions for a user equipment (UE).
FIG. 2 shows an architecture of a system for optimizing handover between a 3GPP network and a high rate packet data (HRPD) network (a CDMA network). An S101 interface is added between an MME and an HRPD access network (HRPD AN) for transmitting signaling messages between the MME and the HRPD AN. A packet data serving node (PDSN) is a user plane processing network element (NE) in the HRPD network, and is adapted to perform user plane processing in the HRPD network.
In the existing technology, a scenario where a UE is handed over between heterogeneous networks may occur. For example, the UE in the HRPD access network is handed over to an E-UTRAN access network.
During the implementation of the present invention, the inventor discovers the following problem in the existing technology: The process of handover between heterogeneous networks in the existing technology, for example, handover between the HRPD network and the E-UTRAN network, does not consider the data lossless processing method, causing a large amount of data loss during the handover process. As a result, the user service is interrupted for a long time and even the user service is completely interrupted, which affects user experiences.